Purification of tar acids



I Patented Feb. 19 1935 I A UNI-TED {OFF IC E 1 a I I {1,9915%9 V 9 ruamloa'riomongrmmuns l ca rl' Eii nartwigjnaybnnan. 1 m Wine BarrettGompanyFNeWIbrlti N5 Y}; woma- -tion -6f-NewJersey w n I "I p mmel-mg, .Application.lulxclfilglfliigiserial I II 1%. 681,167 9 I I I I I 5 10fClaixns. (CH-265M154) I l ll'hisinventionirelamesltmthepurificationoiltarmamacid saltisucheutsodiumacidfisulfate,sodium uaacldsaandsmoizepartimilarlygto asmethodufonre 'ca lrbanateior the-r like, tea-liberate the: tar acids, :movmg iobiectionableiodor :stnom star acids; and- :whichzfloat: anamoilyrlayemonrthe :aqueous salt '.;improving;theimaolorcstahility. solution-awaiting.:etromithezacidtreatment. The

r 5 :;By: :ftarcacidsflzas' usedzinithislspecification, I; -rcrudeiacidnlayerkseparated-bydecantation'for 5 'meanrthe omanicxcyclicmydroxy :compoundswi-for wrectiflcationnon BtOIQEBa-BS desired.

exa-mple,.--;ipheno1, vathe .seresols,."izhe gxylenolsl; erezi hesacids produced -.in-lthe ordinary: way was :h-sultingtrom the destructiveldistillation of. organic 1 .above; -describedareadily idarkenvon rexposure to mattenusuchusasa bituminous @031, "whichmform alightlandehaueeamoflensive edor,=-evennwhen-rel0 sazlts with-icausticsodat-andare capable of heingxfined, wineries-objectionable characteristics great- 10 The term mar .-acids..1 is-used in theclaims in actions.

.. extracted from-.zsolution, in. organic A solvents -..by;,- ly.-lessenl-tlm1value:-of: the'tar acids or make .them

means of aqueouscausticsoda or other aqueous"wcnthlessriommanypurposes. 9

u lalka-linevsol-utionsr: By iicarbolatei.orificarbolate I It is -ianwobjecttot-,imisiinvention to provide a solution? Ii-:meanethe :solution ofareaction1prod-- --vprooess: =forzireflning tarizacids which, results in th.; ncts obtainedby ,ztreating treertarpacids. or .free- 1- substantial-1y mmpleteeremovalr'ofdsuch.objec- 15 ..,,taraacid-bearing material .with. alkaline mateitionahle-ndorzmdiresultsuintarracidsofrimproved .rials -especiallyacaustic.sodas solution. carbolate""lcolomstability. ;-C[!hewprocess;-of. thislzinvention resolutions as wsolute chiefly- (or be; carried outtwithout :seriously-. interfering other; metal, e, zg potassium) salts. of taracids. withwthe ordinary-zymutine -:o f--.-=tar acid "produccomprehensive, 'sense and l ijs intended toinclude I ,i-Incone: methodsoiscarrying out: my 'linvention, tar acids vwhether free.or.inlcomhinatio n-asmetala .1. iagitateatheicarbolatersolution; preferably after salts; a I I II I II n I I II I I 1ilidili tioizi;and nemovalaqt the: neutral oil-by steam It islcustom'r ry to recover-mar acids from-tar-. l-distillation with asmal-l amount of a metal which acid-containing oils'by treating suchoils .witlr:'.willtca useiltnezevolution-loiahydrogen from .alka- 25 an aqueous alkaline solution; these'oilsma'y belineisolutionsgonscontact withmsucmsolutlons I condensates'obtained from' th distillationoicoal -pneter ital-use iromuolzfiepercent to l per cent tar orf'o'f other taracid-producing material. .,bylwgight-of metalcbaaedmonathe :weight of tar Such'oils, commonly called carbol'ic oi1s"3iarymacidsztreated butmayruse upto l0-per-cent or \iiidely in "tar'acid content, dependingo'ntheir more. .a'lIfhe-mixturev isumaintained :at a :tem- 30 source. Carbolic oils resulting from Dy-Product per-attire. tram -1051:0199, C.'.during@the.neaction. coke-oven' operation ordinarily. contain from 7 to Qwingmto i-appreeiableshydrolysis of v :the sodium j'percen byvYolume ofitaryacids, but"wide*val.lphenatesrcarholate solutionsresultingfromcausriationsirom thisrange may occur." fCausticsodag-ticsoda extractiomhave astrong alkaline reacis 'ordinarily employedforthe"'extraction,"'al- ,-.tionQ.vjlI'his isualsomtrue-kotlthel'solutions of tar 35 though other alkaline materials such as caustic acids ingbther vstmngmbases. Furthermore, the -potash or t-heiraqueoussolutions may -=be**em-1.icamholateasolutionsivcommercially..producedfre- *ployedf Thesolution'of-thesodiumsaltsof tar .quentlylcontain a-asmallnexeessmof freemcaustic acids (i. e., the carbolatesolution) is-separatednrsoda.w'llheralkalinitybohthecustomary-commerfrQm -the oii and preferably diluted with -water..Lcialicarbdatesolutions;iwhethernorwnot contain- 40 'and-distilled-ui-th steamto removeneutralhydro-,wingwanexcess offreercausticflsoda,isnsufiicient to carbon material which dissolves in the caustic. neactlwi-thithewsmall amounts of. metal used in solution in appreciable amounts together with carrying. outrun process. (I have ioundlaluminum the-"tar acidsl The .ta-r acid content of" such "dust and zinc dust lefiectiyeireagentsin carrying .zcarbolateresolutions-will .vary'with completeness houtlthisfiprocess; Lpreferttouseizinc dustIsince 45 @encentmy volume of taracidsp Dilution and dis-M-acidification.

of extractionlofxth'e.ioil; strength: of causticzso-L it is mone effective. -After'agitatingthe.carbolate 9 tlution usedcandother.iactors. Commercial-,car- Iwith-the me'taliior a short while, say for. .15 minwbolates, "before distillation with steam; may con- .iiiteszormlongenmiddfilterin, theltaruacidsmay be tain tar acid salts .equivalent to about:35 to recoveredwirom theTfiltefed solution by usua 50 .wtillation with steam to removeneutral 'oil-- re-. AsI anll-alternative procedure aidilute solution wduces the ,tar acid content, for-example to about of amineral acidor' otuanacidsaltl may be added 20 percent by volume. [The :carbolate solutionsato.crude-. or9pa1;tly-refinedfree.taracidsHand the freed of neutral oil is'treated with an acid suchwacidifiedl tan acids agitated with atsmall-amount -;4as suliuricacid-orwith carbon:dioxide; or with -.-oi lafflnelyrdiyided metali suchflaswillcause the evolution of hydrogen on contact with the min eral acid solutions. As in the first modification I may use amphoteric metals such as aluminum or zinc but prefer to use zinc. I may also use such metals as iron, nickel and tin toreact with the acidified tar acids. The tar acids are preferably maintained at the boiling temperature of the reaction solution during the reaction; Upon the completion of the reaction the tar acids are separated by decantation or filtration from the aqueous layer, washed with water and distilled as usual. Where the use of mineral acids is not desirable, the crude taracids containing a small quantity of water, may be 1;reatea im powdered metallic magnesium or calcium instead of with the metals mentioned above, the magnesium re,- acting with the aqueous -"'solu'tion"to' evolve hydrogen.

The following are given as illustrative: examples of the practice of this invention:

Example N0. 1 .-'Ca'rbolatesolution, Y obtained by extracting 'coal tar carbolic oil with caustic soda, was freed from dissolved hydrocarbons and other non-acid impurities by diluting and distilling with steam to give a carbolate containing salts of tar acids equivalent-to about 20 per centby weight of 'tanacids basedon the weight of solution; the carbolate consisted forth'e most part of a solution of the sodiu'msalts of tar acids, the salts of phenol, the'cresols-and -the xylenols predominating; To" one liter of-carbolate were added 2 grams of-ainc dust, equivalent to 1 per cent by weight of the taracid content of the carbolate. The mixture was 'well agitated for 30 minutes and the temperature maintained at approximately 90 C. forabout 3O m'inutesJ The carbolate solution was filtered and thus freed of solid matter, acidified and tar acids'then separated and refined by distillation in 'vacuo.

Example No. 2.To 200 grams crude tar acids were added 50 c. cqoi a"solution of percent sulfuric acid. This amountof acidwas surficient to dissolve completely the "zincdustused in the treatment. The'ac'id formed an aqueous solution that readily settled out from the tar acids after the zinctreatment. ifOne gram of zinc dust".

was added, equivalent toabout 0.5 percent by weight'of 'the tar acids treated. The resultant mixture was boiled under a reflux'condenser for at least minutes or until the evolution of hydrogen had stopped, the boiling in this case furnish-i ing 'sufiicient agitationto effect the desired reaction. The tar acids were separated from the solid residue byfiltration,"washedwith water and distilledin vacuo. Firewater-washing step is'desirable to remove b'y-p r( )d'u'cts of the reaction.

In my co-pending application Serial No. 631,275 I have disclosed a 'methodfo'r purifyinga'ndremoving foreign objectionable odor'fror'n tar acids by treating their alkali and metal "salt solutions with gelatinous metal hydroxides, preferably with iron hydroxide. -Inthat application I'have disclosed that it is desirabl'eto agitate such: a car bolate solution at a temperature of 50 to 90C., with 1 to 2 per cent or more of, for example,

iron hydroxide in orderto improve the odor of the resultantitar" acids. When desired, that method of purificationmaybe' combined with the process disclosed in this specification and more particularly with that modificationjdescribed' in" Example 1, i. e., the carbolate may' be agitated with a gelatinous metal compound toremove impurities and beforeor-after the treatment with gelatinous metal, impurities I may-1pc removed by agitating thecarbol'ate with a metal s'uch as zinc ,for many purposes. The improvement in odor and color stability 'of the tar acids resulting from my method appears to be based on complex re- 1 actions. It may be due to a reduction or hydrogenation of relatively minute quantities of highly unsaturated and reactive pyrogenetic compounds which DQSsibly contain oxygen or sulfur or both.

When tar acids are treated with a metal (e. 3.. go

zinc) .in. acidified solution, as in the'second example given above, the acid treatment and subsequent separation of thelaqueous layer incidentally result inthe removal of baseslii present) in the form of water-soluble salts; if insoluble salts are formed; they are removed in the'filtration step. Since zinc salts areknown-to form addition compounds with tar bases, the use of zinc mayhelp materially'in the removal oithe bases. Among the'b'ases which may be'presentare' '30 pyridine; quinoline, their homologues, and similar nitrogenous compounds."

Without departing- Irom the-scope 01' my invention I may treat in the manner described above not only-carbolate formed by extraoting tar-acid bearing oil but also carbolate formed by dissolvingirnpure acids in' cau'stic'soda or other alka- -line solutions or produced inany other wayfffltar acids and solutions of fr m acids, whemq.

the tar. acids producedby destructive" dis 40 tillationof coal, or by other methods;

It willbe understood that the invention herein is not restricted to the embodiments disclosed, except as defined by the apnended'claiins'j f j "I claim: 7 f .ii i

1'; The method of purifying tarlacids'which [comprises mixing the tar acidsfy'vith a Iree'metal capable of {evolving hydrogen on contact with an acidsolution and agitating theresultant uin?- r ture'.

The method of purifying tar acids comprises treating a carbolate solution. with. a

.free metal capable ofrreacti ng with an aqueous hydroxide solution to cause the evolution oi'iw-v .drogen. mm J.

' which comprise acidifyingtar acids and treating the acidified tar acidwith a metalcapable of re-'--' acting with acid to liberatehydrogen.

6. In the purification of tar acids the step which comprises treatingwith' metallic iron, tar-acids acidified with a mineral acid. 1 1 I I 7. In the purification o1" tar acids the'stepwhich comprises contacting an aqueous mixture containing tar acids with magnesium and agitating the resultant mixture. Y

8. The method of purifying taracids w a free metal capable of reacting with a sodium hydroxide solution to cause the evolution of hydrogen, contacting'the carbolate solution with gelatinous metal hydroxide, separating the solution from solid residue, and liberating the tar acids from the solution.

9. The method of purifying tar acids which comprises contacting a carbolate solution with zinc, adding iron hydroxide to the resulting mix- 10 ture, separating the resulting solution of carbolate from the solid residue, and acidifying the carbolate to liberate the tar acids.

10. The method of deodorizing tar acids and increasing their stability towards light which comprises acidifying tar acids with a mineral acid, treating the resulting mixture with metallic zinc, whereby tar bases are dissolved as salts in the aqueous phase and separating the tar acids from the aqueous phase.

CARL E. HARTWIG. 

